Yahiko must have died and Pain(Nagato) is using his body. The cover of the chapter looks like he's in Deidara's body at the moment.

I think Pain has bodies of his buddies who died, and then Pain goes and kills the people who killed his friends/members for vengeance... He's following Yahiko's dreams of making everyone feel the same pain.

So it's sort of like some spiritual thing where Pain being inside someone else's body is like "BITCH THIS IS WHAT so and so WENT THROUGH! NOW FEEL THE SAME!"

This is his so called judgement.